Propellent cartridge for mortar shells



' 'WVUNITED s'rArss Patented Apr. 5, 1949 2,466,561 PROPELLENT-CARTRIDGE FOR MORTAR SHELLS Application August 22, 1944., Serial No. 550,527

This invention relates to mortar shells used as .propelling andignltion devices'for mortar bombs,

In use a mortar shell is inserted'into a barrel-like protuberance on the'end oi the mortar bomb and the entire bomb is dropped into the-mortar barrel 1 down which it slides until it-hit-s a firing pin located centrally in the bottom of the mortar barrel. The firing pin engages the percussion cap of the mortar shell and the ensuing explosion propels the mortar bomb from the barrel of the mortar. vIn some instances the entire propelling force is provided by the mortar shell while in other instances the mortarshell serves merely as the v 'igniter for rings 'of mortar propellent' powders- I ahatbare fastened on the back end of the mortar om During the early part of the war between the United States and the Japanese during the fight-' 'ing intthe South Pacific Islands'it wasfound that mortar shellsfrequently failed to explode andin'. many instances became unusable. The cause of failure was traced to the high temperatures and high humidity conditions dxisting in the South Pacific Islands-where not infrequently the humidity may peso-90% and even higher, and the temperature well .over 100 F. In other areas of conflict the mortar must-be capable of unvary- 'ing performance even under extremely cold con ditions and accordingly ignition therefore includ A ing the mortar shell propellant and/or ignition device must be capable of unvarying response not only under! extremely. cold conditions, but also ,under extremely warm and moist conditions, even p aftermonths ofstorage.

,Itis an object of the present invention to pro- .vide an. improved mortar shell of rugged and reliable. .construction capable of unvarying and uniforrnjperiormance under extremely wide variations-Iof temperature from well below F. to

wellabove 10093. and under conditions of extreme humidity variation. It is a more specific object of the invention to provide a mortar shell of water andmoisture impervious construction capable of withstanding storage for months at temperatures .weli overil00" E. and under humidity conditions approaching saturation, and ,at the same time capable of withstanding exceedingly cold, dry climatic conditions such as temperatures of 40 I belowzero. It is a specific object of the invention to provide an improved mortar shell of water-. proofand moisture impervious construction capable. of maintaining its gauge throughout its useful life under suchclimatic conditions.

I .Other and further-objects of the invention are 4 Claims. (Cl. 102--39) those inherent in the apparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which Figure 1 is an elevational view partly in section showing the mortar shell of the present invention before being exploded;

Figure 2 is an elevational view partly in section of the mortar shell of the present invention after I being exploded;

- primer i 5. Within the paper tube ill there is a paper liner i6 and base wad or wads H. The paper tube H, as usually constructed, is paraffin impregnated, the liner iii being either unimpregnated or impregnated, as desired. The liner to is preferably terminated at the level l8 and serves as a positioning device for the paper cardboard wad 20. Over the cardboard wad 20 there is positioned a lead wad 22 and over this another cardboard wad 23. The end of the paper tube It) is crimped inwardly as illustrated at 25 so as to retain the wads tightly in place. This much of the construction may be regarded as prior practice.

It was found that shells so constructed without;

the covering cap generally designated 30, hereinafter described-failed when subjected to extreme climatic conditions of temperature and humidity suchas encountered in the South Pacific and riumerou's tests were run utilizing impregnated coat ings of all sorts in an attempt to obtain satisfactory water and moisture resistance. Tests were In accordance with the generally designated 30 which is preferably made of the same material and upon the same machines used in fabricating the cup ii. Cup 35 may conveniently be made upon the same machines as used in fabricating-cup ii. Thus, during mama facture ofcup -il, it isdrawn to the shape of cup 3'0, and then further to form flange i9.

pressed so sis-partially- The cup with the partially. formed flange is placed upon tube ill and pressed on the tube. Hence, cups 30 may conveniently be diverted before any ejector flange is formed, there being at this stage a smoothly rounded shoulder at 3!. The cup 30 is then pressed onto the crimp closed end of the shell tube I and in thepressing operation is drawn down to a. somewhat smaller diameter so as to embed the side wall 32 of the cup into the cardboard material making up the tube Hi. The cup 30 is preferably slightly cham fered inside at the mouth 33 before being assembled onto the shell tube Ill and is beaded in at 34 directly opposite the lead washer 22, thus compressing the cardboard material of tube Ill be? tween the heading 34 and the lead washer. In this way there is a very firm and a very waterproof attachment of the cup 30 to the end of the shell.

For best water and moisture-proofing practice it is desirable to coat the shell 10 with lacquer, varnish, shellac, drying oils, asphalt varnishes, or other water-proofing materials, prior to the assembly of the cup 31] thereon. Inasmuch as the shell tube In is usually prepared of paraflin impregnated paper, the crimp closed shell just before assembly of the cup 30 thereon, may be surface dewaxed in accordance with the method and apparatus set forth in the copending application of William N. King entitled Method of finishing containers impregnated with wax, Ser. No. 550,667, new Patent No. 2,413,144, filed concurrently herewith. In accordance with the method and apparatus of said application the wax is removed from the surface of the crimp closed cartridge and is in a suitable condition for application of water-proofing material which may conveniently be accomplished by dipping the shell into a lacquer bath to a depth so as to cover the entire exposed cardboard tube III, the end wad t3 and a portion at least of the cup H. In the dipping operation of course the shell is inverted from the position shown in Figure 1. The lacquer is then dried, preferably by an oven or radiant heat drying technique, and the cup 30 is then assembled on the shell as previously described. A second coat of lacquer is then applied over the cup 3b, the exposed side wall ofthe tube ill and a portion of the cup II. In order to complete the water-proofing operation the head end It of the cup 1 I is given a dob of waterproofing varnish over the primer cup, thereby sealing the joint between the primer cup i5 and the head portion i l of the cup II. If desired, one or two coats of lacquer may be applied after the cup 36 is in place thereon, after dewaxing the exposed surface of tube l0.

Mortar shells so fabricated are capable of functioning satisfactorily after 48 hours of immersion at a depth of two feet in a water solution containing 3% sodium chloride. The shells likewise withstand three months storage at 85% relative humidity and at a temperature of 115 F.

The shells withstand storage indefinitely at 65 F. 6 There is an inappreciable increase in gauge Figure 2 illustrates the shotgun shell as it appears when fired in a standard mortar. It will be noted that the cup 30 remains in place, the gases from the explosive charge being discharged outwardly through a series of perforations ll, the number and position of which are determined by apertures in the barrel of the mortar bomb in which the shell is used. It maybe stated parenthetically that v the propellant used for mortar bombs is made in the shape oi rings that are mounted on the barrel inwhich the ignition cartridge is positioned and the barrel is. apertured along its side wall so that when the ignition cartridge explodes the hot gases therefrom will be discharged outwardly through the apertures directly into the ring of propellant powder in the outside of the barrel which are then ignited and explode, propelling the bomb from the mortar.

It will be appreciated, of course, that any standard form of crimp such as the unfolded crimp illustrated in Figure 3 may be utilized with the water-proofing and protecting cup 30 of the present invention. Thus, as shown in Figure 3 the tube side wall is unfolded in acres, to form an end crimp 4| over the paper wad 23, lead Wed 22 and paper wad 20. The-entire end of the cartridge is then enclosed by means of the cup generally designated 30 as in Figure 1 and the cup beaded as illustrated at 34 so as to compress the side wall of the tube 40 against the lead wad 22. This construction eliminates all or most of the dead air space 36 of the construction shown in Figure 1;

Likewise, as illustrated in Figure 4, there may be utilized a construction wherein the paper tube of the shell is not crimped at all, being merely plugged by the series of wads, including the paper wad 20, lead wad 22 and the paper wad 23. Over the thus closed end of the shell tube 50 there is then placed the end closure cup generally designated 30 of the type illustrated in Figure l, which is inwardly beaded as illustrated at 34 so as to compress the, tube 50 between the beading 33 and the lead wad 22. In this construction illustrated in Figure 4 the waterproofing depends largely upon the cup 30 and is satisfactory in many instances.

In any of the foregoing constructions by utilizing only one cardboard and wad 23 instead of the paper and lead wads 20, 22 and 23, and by using an exceedingly thin metal or plastic cup 30, or a cup 30 wherein the part 31 is exceedinglythln, the present construction'may be applied satisfactorily to the closure of standard shotgun shells where the propellant gases and load will discharge from the end of the tube rather than through the tube side wallas shown in Figure 2.

When so utilized the cup 30 simply fractures around the corner 3|, the crimp, if used, unfolds and the entire propellant gases, wedding, and load are discharged in the usual manner;

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein except as defined by the appended claims.

What I claim is:

1-. An explosive ammunition .comprising a cylindrical paper tube which is adapted to be fractured when the ammunition is exploded, said tube having an outwardly flanged base closure cup pressed onto one end of the tube, said base closure cup being provided with a percussion cap. an explosive charge, within the tube. an end wad including a stifi disc closing the end of the tube opposite the base closure cup, said end wad being held in place by inwardly crimping of the tube side wall, and a cylindrical closed end waterproofing cup pressed onto the crimped end of the tube, the outer diameter of said cup being substantially the same as the outer diameter of the tube, said cylindrical closed end cup being attached solely by being pressed onto the tube and crimped inwardly circumferentially at a position so as to compress the tube paper against the stiff end wad disc thereby to maintain said cup immovably attached to the tube at explosive pressures sufilcient to rupture the wall of the paper tube.

2. An explosive ammunition comprising a cylindrical paper tube having an outwardly flanged metallic base closure cup pressed onto one end of the tube, said base closure cup being provided with a percussion cap, an explosive charge within the tube, an end wad including a metallic disc closing the end of the tube, said end wad being held in place by a crimp formed in the end of the paper tube side wall, and a thin metal, closed end cylindrical walled closure cup attached to the tubesolely by being pressed and squeezed onto the end of the tube that is closed by said end wad and thereby attached sufllciently to resist displacement when the explosive pressure increases sufiiciently to rupture the side walls of the paper tube.

3. An explosive ammunition comprising a cylindrical paper tube having an outwardly flanged metallic base closure cup pressed onto one end of the tube, said base closure cup being provided with 'a percussion cap, an explosive charge within the tube, an end wad including a metallic disc closing the end of the tube and a thin metal, closed end cylindrical walled closure cup attached to the tube solely by being pressed onto the end of the tube that is closed by said end wad and drawn down in circumference, said closure cup being beaded inwardly at a level substantially coinciding with the position of the metallic disc. 5 4. An explosive ammunition comprising a cylindrical paper tube having an outwardly flanged metallic base closure cup pressed onto one end of the tube. said base closure cup being provided with a percussion cap, an explosive charge Within the tube, an end wad including a metallic disc closing the end of the tube and a thin metal, closed end cylindrical Walled closure cup attached to the tube solely. by being pressed and ,drawn down in circumference onto the end of the tube that is closed by said end wad, said closure'cup being beaded inwardly at a level substantially coinciding with the position of the metallic disc, said ammunition being lacquer coated.

MELVIN J. STANDAL.

-REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 645,546 Blanch Mar. 20, 1900 1,144,379 Pritham June 29, 1915 1,628,527 Brandt May 10, 1927 2,144,232 Spengler Jan. 17, 1939 2,178,599 McCormick Nov. 7, 1939 2,336,065 Cadham Dec. 7, 1943 FOREIGN PATENTS Number Country Date 3,680 Great Britain Feb. 17, 1903 10,192 Great Britain June 16, 1891 203,323 Great Britain Dec. 13, 1923 210,557 Great Britain Feb. '7, 1924 40 

